LIBRARY 

OF  THE  7\ 

UNIVERSITY  OF  CALIFORNIA. 


Class 


The  ABC 


OF 


Railroad  Signaling 


A  Lecture  delivered  before 
the  Harvard  School  of  Bus- 
iness Administration 


BY 

W.  H.   ELLIOTT 
Signal  Engineer  N.  Y.  C.  &  H.  R.  R.  R. 


MACKENZIE-KLINK  PUBLISHING  COMPANY 
CHICAGO 


GENERAL 

C    PREFACE. 


This  little  book  is  intended  to  conduct  the  stu- 
dent, engineer,  or  railroad  officer  who  desires  a 
working  knowledge  of  Signaling  merely  to  the 
entrance  to  its  inner  workings  and  apparently 
mysterious  applications.  It  is  put  forth  to  serve  as 
the  first  step — the  A  B  C  of  Railroad  Signaling. 

It  is  the -earnest  hope  of  the  publishers,  that, 
should  the  learner  desire  to  penetrate  further,  his 
way  will  have  been  made  easier  to  travel,  in  a  meas- 
ure, at  least,  by  the  reading  of  this  first  simple  pres- 
entation of  the  broad  principles  of  the  subject. 

July,  1909. 


Copyrighted  by 
MACKEN/.ir.-Ki.iNK  PUBLISHING  COMPANY 


198850 


THE   ABC 

OF 

RAILROAD   SIGNALING 


Railroad  signaling  is  the  art  of  so  installing  and 
operating  signals  that  an  engineman  may  properly 
control  the  movements  of  his  train  by  the  signal  in- 
dications displayed.  During  the  day  the  signal  in- 
dications are  given  by  the  position  of  the  signal  arm, 
and  at  night  by  the  color  of  a  light.  Owing  to  the 
heavy  and  complicated  construction  required  and 
the  difficulty  in  determining  the  relative  location  of 
a  signal  arm  on  a  pole,  good  practice"  limits  the 
number  of  arms  used  on  a  single  pole  to  three.  Of 
distinctive  lights  that  may  be  used  to  give  the 
signal  indications,  there  are  but  four,  namely,  red, 
yellow,  green  and  purple.  Good  practice  in  the 
safe  and  rapid  movements  of  trains  has  shown  it  is 


6  THE  A  B  C  OF 

desirable  to  give,  either  by  signal  arms  during  the 
day  or  by  colored  lights  at  night,  fourteen  primary 
signal  indications  which  concern  the  immediate 
movement  of  the  train,  and  seven  secondary  indica- 
tions which  have  to  do  with  the  future  control  of 
the  train.  It  will,  therefore,  be  seen  that  in  arrang- 
ing the  signals  and  assigning  a  specific  meaning  or 
indication  to  each  aspect  the  task  has  been  no  easy 
one,  for  if  safe  operation  is  to  be  secured  and  mis- 
takes are  to  be  eliminated,  each  indication  must  be 
definite  and  easily  distinguishable  from  all  the 
others. 

The  practice  of  the  roads  in  the  United  States  in 
the  meaning  assumed  to  be  conveyed  by  various  sig- 
nal aspects,  varies  materially,  and  at  the  present 
time  many  roads  are  changing  their  practice  in  the 
endeavor  to  secure  a  uniform  system  of  signal  in- 
dications. It  is,  therefore,  apparent  that  signaling 
is  not  an  exact  science.  Those  taking  up  the  sub- 
ject at  this  time  must  not  be  surprised  at  finding 
that  different  signal  aspects  on  different  roads  are 
assumed  to  mean  the  same  thing,  or  in  technical 
language,  to  give  the  same  indication. 

Primarily  signaling  has  to  do  with  conveying  to 
the  engineman  the  information  necessary  for  him 
to  safely  and  properly  control  the  movement  of  his 


RAILROAD  SIGNALING 


Hall  disc  signal   indicating  "Clear". 


8  THE  A  B  C  OF 

train.  It  is  assumed  that  with  this  accomplished 
the  engineman  must  do  his  part  and  control  the 
train  in  accordance  with  the  signal  indications  dis- 
played. Various  types  of  signals  are  still  in  use  in 
this  country,  the  semaphore  arm,  the  disc,  and  the 
revolving  banner  type  of  signal.  Of  these  the  sem- 
aphore is  now  recommended  as  the  standard.  The 
semaphore  signal,  as  will  be  seen,  consists  merely 
in  the  attachment  of  an  arm  or  blade  four  feet 
long  to  a  spectacle  which  is  arranged  near  the  top 
of  a  pole  so  that  the  arm  will  stand  normally  in  the 
horizontal  position,  projecting  to  the  right  of  the 
pole,  as  seen  from  an  approaching  train.  To  give 
the  indication  to  proceed,  the  arm  will  be  moved 
downwardly  for  signals  working  in  the  lower  quad- 
rant, and  upwardly  from  the  horizontal  for  signals 
working  in  the  upper  quadrant.  Signals  of  the 
lower  quadrant  type  have  been  the  standard  in  the 
past,  and  the  upper  quadrant  signals  may  be  said  to 
be  the  type  of  the  future.  Six  of  the  larger  roads  of 
the  country  have  adopted  the  upper  quadrant  sig- 
nals as  a  standard  and  it  is  probable  other  roads  will 
do  the  same  in  the  near  future. 

Signals  of  all  kinds  are  divided  into  two  general 
classes :  block  signals,  which  control  the  use  of  a 
section  of  the  track  and  show  whether  or  not  the 


RAILROAD  SIGNALING  9 

track  is  occupied,  and  interlocking  signals,  which 
have  to  do  with  the  switches  in  a  track  and  the  par- 
ticular route  which  is  set  for  a  train  to  take.  With 
interlocking  signals  separate  arms  to  a  maximum  of 
three  are  used  for  indicating  any  one  of  all  possible 


Mechanically  interlocked  home  semaphore  signals  and  a  disc 
signal  on  a  signal  bridge.  Semaphores  in  "Stop"  position.  Disc 
signal  seen  from  rear. 


routes,  the  upper  arm  for  the  main  line  or  through 
route,  the  second  arm  for  a  limited  speed  route  from 
one  track  to  another  with  traffic,  and  the  third  and 
lowest  arm  for  any  one  of  all  possible  routes.  With 
block  signals,  but  two  arms  are  used  on  a  pole,  the 
upper  arm  to  indicate  immediate  and  present  con- 


10  THE  A  B  C  OF 

trol  as  to  whether  or  not  the  train  may  pass  the 
signal,  and  the  lower  arm  to  repeat  the  indication 
of  the  upper  arm  of  the  next  signal  in  advance. 

In  block  signaling  the  track  is  divided  into  a  num- 
ber of  sections  of  considerable  length,  which  sec- 
tions are  termed  "blocks."  At  the  commencement 
of  each  section  a  signal  is  placed,  which  is  called  a 
block  signal.  This  signal  is  also  known  as  the  home 
signal,  as  it  governs  the  movement  of  the  train  when 
entering  the  block.  The  signal  which  is  used  to 
repeat  the  indication  of  the  next  signal  in  advance 
is  called  the  distant  signal.  For  blocks  that  are  one 
and  one-half  miles  in  length,  or  shorter,  the  distant 
signal  is  usually  placed  on  the  same  pole  with  the 
home  signal.  When  the  blocks  are  longer  than 
this,  the  distant  signal  is  usually  placed  on  a  sep- 
arate pole  located  about  3,500  feet  in  the  rear  of  the 
home  signal.  This  distance  for  level  track  is  suffi- 
cient to  enable  a  train  traveling  at  a  speed  of  75 
miles  an  hour,  or  less,  to  be  stopped  in  running  be- 
tween the  distant  and  the  home  signal,  a  requisite 
necessary  for  the  safe  and  proper  control  of  a  train. 
When  the  home  signal  arm  is  in  the  horizontal  po- 
sition, "stop"  is  indicated.  When  the  arm  is  60  de- 
grees below  the  horizontal  or  90  degrees  above  the 
horizontal,  "proceed,  block  is  clear"  is  indicated.  If 


RAILROAD  SIGNALING  11 

there  are  two  arms  on  the  pole,  the  upper  arm  is  the 
home  signal,  and  when  in  the  proceed  position  in- 
dicates the  train  may  proceed  through  the  block  to 
the  next  signal  in  advance.  If  the  upper  arm  and 
the  lower  arm  are  both  at  clear,  an  indication  is  also 
given  that  the  next  home  signal  or  the  one  at  the 


Electrically   operated    interlocked   semaphore   signals  on    a   sig- 
nal bridge.     Upper  blade  indicates  "Proceed  on  main  line  route". 


commencement  of  the  second  block  in  advance  is  at 
clear  and  the  train  may  proceed  for  two  blocks  in 
advance.  In  this  way  an  engineman  finding  both 
arms  of  a  signal  at  clear  may  proceed  at  speed, 
knowing  that  a  distant  signal  will  be  passed  which 
will  give  ample  warning  in  time  to  enable  him  to 
properly  control  the  speed  of  the  train,  should  there 
be  a  signal  in  advance  which  is  indicating  stop. 


12  THE  A  B  C  OF 

Block  signal  systems  are  divided  into  three  gen- 
eral classes : 

1 — The  telegraph  system,  so  named  from  the 
means  employed  in  conveying  from  one  station  to 
the  next  information  as  to  the  state  of  the  block. 

2 — The  controlled  manual  system,  so  named  from 
the  fact  that  while  the  signal  at  the  entrance  to  the 
block  is  cleared  by  a  signalman,  the  clearing  of  the 
signal  is  controlled  by  the  signalman  at  the  outgo- 
ing end  of  the  block,  who  must  first  give  an  unlock 
for  the  signal  before  it  may  be  cleared  for  a  train 
to  enter  the  block. 

3 — The  automatic  signal  system,  so  named  from 
the  fact  that  the  signals  are  operated  by  some  form 
of  power,  and  being  automatic  in  action,  do  not  have 
to  be  worked  by  an  attendant.  The  automatic  sys- 
tems are  further  classed  according  to  the  power  em- 
ployed to  work  the  signals.  With  the  electro-pneu- 
matic system  compressed  air  is  the  power  used  and 
electricity  is  employed  to  control  the  action  of  the 
compressed  air.  In  the  electric  system  direct  cur- 
rent is  used  to  energize  the  motor  which  turns  and 
clears  the  signal,  and  also  to  work  the  relays  and 
circuits  of  the  controlling  system,  causing  the  sig- 
nal to  give  the  proper  indications.  In  the  alter- 
nating current  electric  system  the  controlling  and 


RAILROAD  SIGNALING 


13 


the  motor  circuits  are  worked  by  alternating  cur- 
rent which  must  be  obtained  from  a  power  house 
and  be  distributed  on  a  specially  arranged  wire  line. 


Automatic  block  signals,  electrically  operated,  upper  blade  in- 
dicates "Block  ahead  is  clear", — lower  blade  is  a  distant  signal 
for  the  upper  blade  on  the  next  signal  ahead,  repeating  its  posi- 
tion. In  the  illustration  the  lower  blade  indicates  that  the  second 
bock  ahead  is  "Clear". 


14  THE  A  B  C  OF 

In  the  telegraph  block  system  signal  stations  are 
located  at  convenient  points  to  give  the  desired 
spacing  of  trains,  and  signals  are  placed  to  govern 
trains  moving  in  each  direction.  As  the  signal  to 
govern  trains  moving  in  a  certain  direction  must 
project  to  the  right  of  the  pole,  as  seen  from  an  ap- 
proaching train,  the  two  signal  arms  required  to 
govern  for  both  directions,  where  there  are  but  one 
or  two  tracks,  are  sometimes  placed  on  the  same 
pole.  A  stand  with  a  lever  for  each  signal  to  be 
worked  is  placed  in  the  station  office  and  a  telegraph 
wire  is  installed  with  the  necessary  instruments. 
With  the  telegraph  block  system  distant  signals  are 
not  usually  installed,  but  where  the  operating  con- 
ditions, such  as  a  down  grade  track,  an  obstructed 
view  of  the  signal,  or  the  high  speed  of  trains  make 
it  necessary  that  the  engineman  be  informed  in  ad- 
vance of  the  indication  given  by  the  block  signal,  a 
distant  signal  is  often  used. 

With  the  equipment  installed  at  each  station  and 
signalmen  provided,  the  blocking  of  trains  must  be 
performed  in  accordance  with  the  rules  which  each 
road  adopts  for  its  own  use.  On  the  approach  of 
a  train  to  a  station  the  signalman  examines  the  block 
record  on  which  is  marked  the  time  each  train  en- 
ters the  block,  passing  the  station  in  the  rear,  the 


RAILROAD  SIGNALING 


15 


time  the  train  passes  the  station  at  which  the  sig- 
nalman is  located,  and  the  time  the  train  passes  the 
station  in  advance,  and  if  the  block  is  shown  to  be 


I 


Single  blade  automatic  block  signal  giving  "Clear"   indication. 
This  indication   is  in  the  lower  right  hand  quadrant. 


16  THE  A  B  C  OF 

clear,  that  is,  that  the  last  train  entering  has  been 
reported  as  leaving  the  block,  then  the  signal  is 
cleared  and  an  approaching  train  may  enter  the 
block  without  reducing  speed.  As  soon  as  the  head 
end  of  a  train  has  passed  the  signal,  the  signalman 
reports  to  the  next  station  in  advance  the  time,  to- 
gether with  the  number  of  the  train.  On  the  rear  of 
the  train,  which  is  the  car  having  the  markers,  pass- 
ing the  signal  and  traveling  for  300  to  500  feet  be- 
yond the  signal,  the  signalman  reports  to  the  man  in 
the  station  in  the  rear  that  the  block  is  clear.  The 
time  so  reported  is  marked  on  the  block  record  and 
on  the  train  being  reported  as  having  passed  the 
block  station  in  advance,  the  fact  must  also  be 
marked  on  the  block  record  and  the  block  will  then 
be  clear  and  another  train  may  be  admitted. 

On  single  track  it  is  necessary,  before  a  train  may 
be  admitted  to  the  block,  to  communicate  to  the  sig- 
nalman at  the  other  end  of  the  block  to  have  him 
lock  his  signal  in  the  position  indicating  stop,  and  to 
keep  trains  from  entering  the  block  from  that  direc- 
tion until  the  expected  train  has  arrived. 

Where  there  are  more  trains  to  be  run  than  may 
be  permitted  to  pass  on  a  single  track,  if  one  train 
only  is  allowed  to  occupy  a  block  at  a  given  time,  it 
is  customary  on  many  lines  to  allow  two  trains  to 


RAILROAD  SIGNALING 


17 


be  in  a  block  at  the  same  time.  If  one  train  only  is 
allowed  in  a  block,  it  is  termed  "absolute  blocking." 
If  two  or  more  trains  are  permitted  in  a  block  it  is 
said  to  be  "permissive  blocking."  Permissive  block- 
ing is,  in  many  instances,  allowed  in  the  running  of 


Base  of  an  automatic  block  signal  showing  one  method  of 
constructing  a  foundation  for  the  signal  post.  The  box  on  the 
post  contains  the  relays  which  govern  the  signal  mechanism. 
The  primary  batteries  which  furnish  current  for  the  operation 
of  the  signal  are  housed  in  the  foundation.  Bond  wires  for  the 
electrical  connection  from  one  rail  to  another  may  be  noted  in 
the  lower  right  hand  corner  of  the  picture. 

freight  trains,  but  where  a  passenger  train  is  con- 
cerned absolute  blocking  is  almost  always  enforced, 
except  in  a  case  of  an  emergency.  While  permissive 


18  THE  A  B  C  OF 

blocking  may  be  allowed  on  certain  roads  as  a  gen- 
eral practice,  it  is  usually  the  case  that  when  the 
weather  conditions  are  bad  on  account  of  fog,  snow 
or  storms,  the  dispatcher  may  require  that  absolute 
blocking  be  observed.  It  may  also  be  required  that 
on  portions  of  the  line  where  the  operating  condi- 
tions are  difficult  absolute  blocking  may  be  enforced. 
The  practice  on  the  various  roads  regarding  this 
differs  materially,  and  it  must  be  assumed  that  each 
road  follows  the  practice  it  finds  best  to  meet  the 
existing  conditions. 

With  telegraph  blocking  a  check  upon  the  work 
of  the  signalman  is  not  provided,  and  if  he  should 
fail  to  enter  on  the  record  the  time  of  a  train  enter- 
ing or  leaving  a  block,  two  trains  may  wrongly  be 
allowed  to  be  in  a  block  at  the  same  time,  both  hav- 
ing received  clear  signals,  indicating  there  was  no 
other  train  in  the  block.  A  signalman  may  fail, 
through  error  or  neglect,  to  communicate  with  the 
man  at  the  other  end  of  the  block  and  may  admit  a 
train  when  the  block  was  occupied.  Wherever  men 
are  employed  they  will  occasionally  make  mistakes, 
and  to  guard  against  a  thing  of  the  kind  happening 
and  possibly  an  accident  resulting,  the  controlled 
manual  system  of  blocking  trains  has  been  perfect- 
ed. In  this  system  an  electric  lock  is  placed  on  the 


RAILROAD  SIGNALING 


The  mechanism  of  the  Union  Switch  and  Signal  Company's 
Style  B  automatic  signal.  The  rods  are  connected  to  the  sema- 
phore. It  will  be  observed  that  were  the  mechanism  shown  in 
use,  the  semaphore  to  which  the  rear  rod  is  connected  would  be 
in  the  "Stop"  position,  while  the  semaphore  to  which  the  rod  in 
the  front  of  the  picture  is  connected  would  be  indicating  "Clear". 


20  THE  A  B  C  OF 

lever  working  the  signal  at  the  entrance  end  of  the 
block,  and  an  electric  switch  with  which  the  lock 
circuit  is  controlled  is  placed  at  the  station  at  the 
outgoing  end  of  the  block.  When  the  circuit  to  the 
lock  is  open,  the  lever  is  locked  and  when  this  cir- 
cuit is  closed,  the  lever  is  unlocked.  This  makes  it 
necessary  that  the  two  signalmen,  the  one  at  the 
entrance  and  the  other  at  the  outgoing  end  of  the 
block,  must  co-operate  in  the  clearing  of  the  signal. 
The  signal  at  the  entrance  of  the  block  is  manually 
operated,  the  same  as  with  the  telegraph  block  sig- 
nal, but  is  also  controlled  by  the  man  at  the  other 
end  of  the  block  through  the  working  of  the  electric 
lock,  hence  the  derivation  of  the  name  by  which 
the  system  is  known. 

Although  controlled  .by  both  signalmen,  it  would 
be  possible  for  both  to  work  together  and  wrongly 
clear  the  signal  if  some  additional  apparatus  was 
not  provided  to  prevent  this.  To  guard  against  this 
being  done,  controlling  track  circuits  are  installed 
at  each  station  and  a  block  instrument  has  been  de- 
signed which,  when  a  train  passes  a  signal  and  en- 
ters the  block,  opens  the  circuit  to  the  lock  on  the 
signal  lever  and  prevents  the  second  clearing  of  the 
signal  until  the  train  has  passed  over  the  track  cir- 
cuit at  the  outgoing  end  and  therefore  out  of  the 


RAILROAD  SIGNALING 


block.  To  insure  that  the  electric  lock  may  become 
effective  and  lock  the  signal  in  the  stop  position,  the 
circuits  are  so  arranged  that  before  the  circuit  to  the 
lock  of  the  station  in  the  rear  may  be  completed, 
the  signal  at  the  station  from  which  release  is  given 
must  first  be  put  in  the  stop  position.  Immediately 


Home  signal  indicating  "Stop".  Distant  signal  indicating 
"You  may  expect  to  find  the  next  home  signal  indicating  either 
•Stop'  or  'Clear'." 

this  is  done  the  electric  lock  on  the  lever  will  drop 
into  the  notch  in  the  lever,  locking  the  lever,  and 
with  it  the  signal,  should  the  block  in  advance  be 
occupied. 

Owing  to  the  convenience  and  quickness  in  hand- 
ling, communication  between  block  stations  of  the 
controlled  manual  system  is  generally  had  by  means 


22  THE  A  B  C  OF 

of  bells,  a  proper  code  being  arranged.  On  a  train 
approaching  a  block  station  the  signalman  rings  the 
next  station,  requesting  an  unlock  of  his  signal.  If 
the  block  is  clear  the  signalman  at  the  station  in 
advance  works  the  block  instrument  by  pulling  the 
plunger  lever  which  closes  the  circuit  to  the  lock  of 
the  station  in  the  rear,  indicating  to  that  sig- 
nalman that  the  signal  may  be  cleared.  On  plung- 
ing, the  card  or  dial  in  the  block  instrument  which 
previously  indicated  "free"  is  changed  to  show  the 
word  "locked,"  indicating  that  the  instrument  is 
locked,  and,  permission  having  been  given  for  train 
to  enter  the  block,  a  second  permission  or  plunging 
action  cannot  be  performed.  When  the  signal  has 
been  cleared  and  the  train  enters  the  block,  the  cir- 
cuit to. the  lock  is  broken  and  the  indicator  of  the 
block  instrument  in  the  station  in  advance,  which 
previously  stood  at  "locked"  now  drops  to  show 
''train  in  block."  This  indicates  to  the  signalman  in 
that  station  that  a  train  is  approaching  and  he  pro- 
ceeds to  get  an  unlock  from  the  station  in  advance 
and  to  clear  the  signals  at  his  station  when  the  un- 
lock has  been  received.  On  the  train  passing  off  of 
the  track  circuit  and  out  of  the  block,  and  the  sig- 
nalman has  returned  the  home  signal  to  the  stop 
position,  the  card  of  the  block  instrument  drops  to 


RAILROAD  SIGNALING  23 

"free"  and  the  signalman  may  again  plunge  and  re- 
lease the  signal  at  the  station  in  the  rear  for  another 
train  to  enter  the  block. 

As  a  further  check  on  the  work  of  the  signalman 


mam 


Upper    quadrant    signal    indicating    "Proceed    at    limited    speed". 

to  prevent  his  making  a  mistake,  it  is  customary  to 
put  an  electric  slot  or  releasing  device  in  the  signal 
connection  to  insure  that  the  signal  will  go  to  the 
stop  position  automatically  when  the  train  passes 
the  signal  and  thus  force  the  signalman  to  restore 


24  THE  A  B  C  OF 

the  lever  to  the  normal  position  to  again  get  control 
of  the  signal,  in  which  case  the  block  being  occupied, 
the  electric  lock  will  hold  the  lever  and  prevent  the 
clearing  of  the  signal  again  until  the  block  is  clear. 
The  controlled  manual  system  without  a  track 
circuit  from  one  block  station  to  the  next  may  oc- 
casionally fail  and  a  wrong  clear  indication  be  given. 
If  a  track  circuit  is  installed  the  manual  control  of 
the  signals  except  for  special  situations,  may  as  well 
be  eliminated  and  the  signals  made  automatic  in 
action  with  less  complication  in  apparatus  and  fewer 
failures.  The  blocks  may  then  be  made  short  to 
allow  for  a  maximum  traffic,  and  when  there  is  a 
failure,  the  detentions  of  trains  are  reduced  to  a 
minimum  compatible  with  safety.  In  the  automatic 
system  the  signals  are  power  operated,  and  in  the 
more  common  forms  are  worked  by  direct  current 
or  by  compressed  air.  With  either  type,  the  control 
of  the  power  is  effected  by  means  of  relays,  a  very 
common  form  of  which  is  found  in  the  mechanism  of 
the  electric  bell,  which,  instead  of  being  fitted  with 
a  clapper  and  striking  a  bell,  is  provided  with  con- 
tacts which,  in  the  case  of  the  motor  operated  sig- 
nal, open  and  close  the  circuit  to  the  motor,  causing 
it  to  move  the  signal  arm  to  the  position  to  give  the 
proceed  indication  when  the  motor  is  energized,  and 


RAILROAD  SIGNALING 


25 


to  allow  the  signal  to  assume  the  stop  position  when 
the  motor  circuit  is  open.  The  circuit  of  this  motor 
control  relay  and  the  corresponding  circuits  are 
known  as  line  or  signal  circuits  to^distinguish  them 
from  the  track  circuits. 


f 

1; 


A  double  automatic  signal  location.  The  train  on  the  right 
hand  track  has  just  entered  the  block,  and  the  signals  have, 
therefore,  just  assumed  the  "Stop"  position.  Signals  on  the  left 
hand  are  indicating  "Two  Blocks  Clear"  for  a  train  running  in 
the  direction  opposite  to  that  of  the  train  shown, 


26  THE  A  B  C  OF 

In  the  automatic  signal  system  the  control  of  the 
signal  circuits  and  therefore  of  the  signals  and  the 
system,  is  obtained  through  the  operation  of  a  track 
circuit  of  low  potential  of  which  the  rails  are  made 
to  form  a  part.  The  track  is  divided  into  sections  of 
a  length  suitable  for  track  circuit  purposes,  3,000 
feet  being  possible  where  the  track  is  gravel  bal- 
lasted, and  5,000  feet  for  a  track  having  rock  ballast. 
One  section  is  separated  from  the  other  by  means  of 
an  insulating  rail  joint,  placed  at  the  end  of  each 
rail  of  each  section.  At  one  end  of  the  section  a 
battery  is  placed,  usually  consisting  of  two  gravity 
cells  connected  in  parallel  to  give  the  maximum  out- 
put in  quantity  of  current  or  amperes,  at  a  minimum 
voltage.  The  rails  of  the  track  are  connected  to- 
gether electrically  by  two  wires  placed  at  each  joint, 
these  being  known  as  bond  wires.  At  the  other  end 
of  the  section  of  rails  from  the  battery  end,  a  relay 
is  placed  having  connections  to  the  ends  of  the  rails. 
The  current  from  the  battery  passes  from  the  pos- 
itive pole  to  the  rail  to  which  the  copper  element  is 
attached,  through  that  rail  to  the  other  end  of  the 
section,  from  this  rail  to  the  relay,  through  the  relay, 
energizing  it,  to  the  other  or  negative  rail  and  back 
through  that  rail  to  the  negative  pole  of  the  battery. 
The  voltage  of  the  battery  is  made  low  to  reduce  to 


RAILROAD  SIGNALING 


27 


a  minimum  the  leakage  between  rails,  as  the  insula- 
tion afforded  by  the  ties  is  very  low,  particularly  in 
wet  weather.  The  resistance  of  the  relay  is  also 
made  low,  generally  four  ohms,  to  insure  that  suffi- 
cient current  will  pass  through  the  relay  to  energize 
it  when  the  track  is  not  occupied. 


Electrically    operated    interlocked    home    signals    governing    a 
terminal   track  arrangement.     All   signals  are  indicating   "Stop". 


With  the  relay  energized  the  armature  is  attract- 
ed, closing  the  contacts  and  completing  the  line  or 
signal  circuit,  which  in  turn  energizes  the  motor 
control  relay,  closing  the  motor  circuit  and  causing 
it  to  operate  to  clear  the  signal.  If,  with  the  signal 
at  clear,  a  train  passes  the  signal,  running  on  to  the 
track  circuit,  the  wheels  of  the  train  offer  a  path  of 
practically  zero  resistance,  and  the  current  from  the 


28  THE  A  B  C  OF 

battery  flows  from  one  rail  to  the  other  through  the 
wheels  of  the  train,  shunting  the  relay,  and  de-en- 
ergizing its  armature,  causing  it  to  fall  away  from 
the  poles  and  open  the  line  or  signal  circuit.  On 
the  opening  of  this  circuit,  the  relay  controlling  the 
circuit  to  the  motor  and  signal  mechanism  is  de- 
energized,  releasing  the  mechanism  and  causing  the 
signal  to  indicate  stop,  which  when  interpreted 
means  that  there  is  a  train  in  the  block. 

Where  there  is  but  one  track  circuit  and  one  sig- 
nal, the  track  relay  may  be  made  to  control  the  sig- 
nal motor  circuit  direct,  but  if  there  are  two  or  more 
track  circuits  in  the  block  if  distant  signals  are  em- 
ployed, or  if  other  agencies  are  used  than  a  motor 
to  work  the  signal,  the  track  relay  does  not  possess 
sufficient  power,  owing  to  the  weak  current  it  is 
necessary  to  use,  and  line  or  signal  circuits  must  be 
used  for  this  purpose.  These  line  circuits  are  em- 
ployed to  ring  bells  at  crossings,  work  indicators,  re- 
peaters and  others  of  the  numerous  auxiliary  de- 
vices which  are  used  in  connection  with  an  auto- 
matic signal  system. 

In  the  electro-pneumatic  system  compressed  air 
at  75  pounds  pressure  is  used  to  work  the  signals 
In  other  respects  the  system  is  the  same  as  the  di- 
rect current  electric  system.  The  signal  relay  by 


RAILROAD  SIGNALING 


29 


which  the  working  of  the  signal  is  controlled  is,  in 
this   instance,   not   provided   with   contacts   but  in- 


The  automatic  disc  signals  shown  here  govern  the  block  im- 
mediately ahead  and  the  semaphore  arms  repeat  the  positions  of 
the  next  home  signals  in  advance.  The  first  and  third  signals 
counting  from  the  left  govern  trains  running  on  the  first  and 
third  tracks  toward  the  bridge  in  the  background,  while  the 
second  and  fourth  signals  govern  trains  running  on  the  second 
and  fourth  tracks  in  the  opposite  direction. 


30  THE  A  B  C  OF 

stead,  the  armature  is  made  to  act  as  a  pin  valve  to 
supply  or  to  shut  off  the  air  to  a  cylinder,  the  piston 
of  which  is  connected  to  the  signal. 

When  air  is  admitted  to  the  cylinder  in  the  elec- 
tro-pneumatic system  the  signal  is  made  to  assume 
the  clear  position.  When  the  air  supply  to  the 
cylinder  is  shut  off  and  an  escape  to  the  atmos- 
phere opened,  the  weight  of  the  signal  forces  the 
air  from  the  cylinder  and  the  signal  is  changed 
to  the  horizontal  position  indicating  stop. 

With  the  electro-pneumatic  system  is  is  neces- 
sary that  compressors  be  put  in  at  every  25  or  30 
miles  of  road  and  the  compressed  air  distributed  by 
a  main  pipe  line.  Where  signals  are  located,  a  tap- 
on  the  main  pipe  is  made  and  connections  to  the 
signals  are  put  in.  Care  has  to  be  used  in  collect- 
ing all  condensed  water  from  the  compressed  air. 

With  the  introduction  of  electric  train  service 
on  steam  operated  railroads  and  the  rails  are  used 
for  the  return  of  propulsion  current  to  the  power 
house,  it  is  not  possible  to  use  battery  operated  track 
circuits  to  control  the  signals,  and  the  alternating 
track  circuit  has  been  designed  to  answer  the  same 
purpose.  In  this  circuit,  the  relay  consists  merely 
of  an  induction  motor,  the  armature  of  which  on 
revolving  is  made  to  close  or  open  contacts  to 


RAILROAD  SIGNALING 


31 


control  signal  or  motor  circuits.  The  current  for 
the  track  circuit  being  alternating  must  be  obtained 
from  a  power  station  and  the  current  distributed 
on  a  suitable  line  at  a  comparatively  high  voltage. 
Where  there  are  signals  to  be  worked  and  track 


Three-quarter  and  sectional  view  of  the  controlled  manual  sig- 
nal mechanism  made  by  the  General  Railway  Signal  Company. 
The  signal  is  cleared  by  manipulation  of  the  handle  shown  in 
the  first  picture,  under  the  proper  circumstances. 


circuits  to  be  operated,  a  transformer  is  connected 
to  the  line  which  transforms  the  high  to  the  lower 
voltage  current  required.  The  ohmic  resistance  be- 
tween the  rails  being  low,  a  low  voltage  current  is 


32  THE  A  B  C  OF 

used,  although  there  is  no  objection  to  using  slight- 
ly higher  voltages  with  alternating  current  than 
with  direct  current,  the  leakage  with  the  alternat- 
ing current  being  much  less.  The  particular  volt- 
age used  in  each  case  will  depend  on  the  length  of 
track  circuit  and  the  insulation  between  the  rails, 
the  current  potential  varying  from  1  to  12  volts  or 
even  higher,  when  necessary.  Insulating  splices  are 
used  to  separate  the  track  circuits  one  from  the 
other,  the  same  as  with  D.  C.  circuits,  but  as  the 
rail  must  be  used  for  the  return  of  propulsion  cur- 
rent, a  path  for  this  current  must  be  provided  while 
isolating  or  keeping  separate  each  track  circuit  cur- 
rent. This  may  be  done  in  a  number  of  ways,  the 
most  common  being  to  use  one  rail  for  the  signal 
A.  C.  circuit  alone,  and  the  other  rail  for  the  other 
side  of  the  track  circuit  and  also  for  the  propulsion 
current,  in  which  case,  this  common  rail  is  con- 
tinuous and  insulating  rail  joints  are  put  in  only  in 
the  rail  given  up  for  the  signal  track  circuit. 

The  other  arrangement  of  A.  C.  track  circuit 
that  is  in  common  use  is  the  one  where  both  rails 
of  the  track  are  used,  both  for  direct  current  pro- 
pulsion and  for  alternating  current  track  circuits. 
At  each  end  of  the  track  circuit  a  reactance  bond 
is  placed  having  terminals  which  connect  the  bond 


RAILROAD  SIGNALING 


33 


with  the  ends  of  each  of  the  track  circuit  rails. 
This  bond  is  of  comparatively  low  resistance  to  the 
passage  of  the  propulsion  current,  which  therefore 
flows  almost  as  readilv  as  if  the  rail  were  continuous 


Sketch  showing  in  full  lines  the  position  of  a  Relay  armature 
and  the  arrangement  by  which  a  circuit  is  closed  when  the 
relay  electro-magnet  coils  are  energized  by  the  passage  of  the 
current  through  them,  and  in  dotted  lines  the  position  of  the 
armature  and  the  broken  circuit,  when  the  relay  coils  are 
de-energized. 


and  without  insulating  joints.  To  an  alternating 
current  the  bond  is  reactive  giving  a  resistance 
in  proportion  to  the  number  of  turns  in  the  coil 
and  to  the  size  of  the  iron  core.  By  making  the 
reactive  resistance  in  the  bond  sufficient  to  give  a 


34  THE  ABC  OF  •       1 

difference  in  potential  at  the  end  of  the  track  sec- 
tion sufficient  to  work  the  relay,  the  relay  will  be 
operated  the  same  as  if  there  was  no  electrical 
connection  between  the  ends  of  adjacent  track  cir- 
cuits, and  both  rails  of  the  track  may  in  this  way 
be  successfully  used  both  for  propulsion  and  alter- 
nating current  track  circuits. 

Where  the  propulsion  current  is  alternating  as 
well  as  the  current  used  for  track  circuit  purposes, 
it  is  necessary  that  the  two  currents  differ  in  fre- 
quency of  alternating  sufficiently  to  prevent  the 
propulsion  .current  from  having  any  effect  on  the 
track  circuit  relay,  the  armature  of  which  must 
respond  only  to  the  track  circuit  current.  A  cur- 
rent of  25  cycles  per  second  is  the  one  usually 
employed  for  propulsion  current,  and  by  making 
the  frequency  of  the  track  circuit  current  40  cycles 
or  60  cycles  per  second  the  impulses  to  turn  the 
armature  of  the  track  circuit  relay,  while  occurring 
at  the  same  instant  for  at  least  one  cycle  out  of 
the  total  given  in  one  second,  will  so  soon  change 
and  be  opposing  each  other  in  pull  on  the  armature, 
that  the  armature  will  react  and  will  be  turned  only 
by  the  current  having  the  frequency  for  which  the 
motor  is  arranged  to  work. 


RAILROAD  SIGNALING  35 

With  a  constant  supply  of  current  at  all  points 
of  the  line,  such  as  is  necessary  where  A.  C.  track 
circuits  are  installed,  it  is  economical  and  usually 
the  practice  to  use  this  current  for  all  circuits  and 
dispense  with  batteries  and  the  care  necessary  in 
their  maintenance.  Alternating  current  is  therefore 
used  to  work  the  signals,  the  signal  circuit  and 


Sketch  showing  the  principal  connections  for  a  track  circuit 
in  a  single  section,  the  arrows  indicating  the  direction  of  the 
current  flow. 


practically  do  all  the  work  of  operating  the  entire 
signal  system.  As  a  failure  of  tne  power  supply  will 
put  the  entire  system  out  of  service,  it  is  necessary 
that  provision  be  made  for  a  constant  supply  of 
current.  Complete  equipment  in  duplicate  for  the 
principal  parts  is  usually  installed  in  the  power 
stations  and  every  precaution  is  taken  to  prevent  a 
drop  in  the  voltage  or  a  stoppage  of  the  current. 
The  block  signaling  of  a  line  of  road  requires  a 


36  THE  A  B  C  OF 

knowledge  of  the  traffic,  grades,  the  location  of 
switches,  curves,  stations  and  objects  which  will 
obstruct  a  view  of  the  signals  from  approaching 
trains.  As  near  as  practicable,  the  signals  should 
be  located  to  permit  trains  running  at  speed  to 
follow  each  other  through  the  consecutive  blocks  in 
practically  the  same  interval  of  time.  If  the  blocks 
were  made  of  equal  length,  trains  would  be  spaced 
equal  distances  apart,  but  very  unequally  spaced  as 
to  time  where  the  grades  in  one  case  were  ascend- 
ing and  in  the  other,  descending.  One  train  would 
then  often  overtake  the  other,  causing  delay  and  a 
useless  expenditure  of  fuel.  The  average  length  of 
*»  block  should  be  based  on  the  number  of  trains  it  is 
desired  to  run  in  a  given  time.  Blocks  one  mile 
long  are  considered  good  practice  for  roads  having 
as  many  as  30  trains  per  track  per  day.  Longer 
blocks  may  be. and  are  used  up  to  as  much  as  3 
miles  in  length,  but  owing  to  the  time  lost  by  a 
train  in  running  through  the  block  when  there  is 
a  signal  failure,  it  is  not  advisable  to  make  the 
blocks  longer  than  2  miles. 

Having  determined  on  the  average  length  of  block 
desired,  and  before  locating  the  signals  in  the  field 
it  is  best  to  draw  a  plan  of  the  tracks  and  make 


RAILROAD  SIGNALING 


37 


a  proposed  location  of  the  signals,  in  which  the 
length  of  the  block  will  be  increased  in  the  propor- 
tion that  the  grade  of  the  track  is  descending  and 
shortened  for  an  ascending  grade.  Where  there 
are  switches,  the  signals  should  be  located,  if  prac- 
ticable, in  the  rear  of  the  switch  and  at  curves,  so 


An    interlocking   tower  governing   a  complicated   terminal   yard 
and  depot  arrangement  of  tracks. 


that  the  signals  may  be  seen  by  an  approaching 
train.  It  is  also  desirable  that  the  signals  for  dif- 
ferent tracks  be  placed  near  the  same  points  to 
economize  in  cost  of  installation  and  maintenance. 
The  exact  location  of  the  signals  along  the  track 
should  be  made  only  after  the  ground  has  been 


38  THE  A  B  C  OF 

looked  over  carefully  and  all  of  the  varying-  ele- 
ments which  enter  into  the  problem  have  been  con- 
sidered. Poorly  located  signals  will  result  in  an 
uneven  spacing  of  trains  and  render  difficult  the 
work  of  the  engineman  in  properly  controlling  the 
movement  of  his  train. 

While  it  is  comparatively  easy  to  locate  signals 
where  the  blocks  are  a  mile  in  length,  the  problem 
becomes  difficult  where  the  blocks  are  made  short 
to  accommodate  a  maximum  traffic.  In  such  cases 
the  shortest  length  of  block  that  may  satisfactorily 
be  used  is  that  of  the  braking  distance  for  the  speed 
at  which  trains  are  required  to  run.  In  every  case 
it  is  necessary  for  safe  operation  that  the  distant 
signal  be  placed  far  enough  from  the  home  signal 
for  a  train  running  at  the  maximum  speed  allowed 
to  come  to  a  stop  in  the  distance  between  the  dis- 
tant and  the  home  signal.  If  this  is  not  done,  then 
in  bad  weather, -when  the  distant  signal  cannot  be 
seen  until  the  engineman  arrives  at  the  signal,  he 
must  either  slow  down  to  be  able  to  stop  at  the 
home  signal,  should  the  distant  signal  be  indicating 
caution,  or  else,  run  the  chance  of  going  by  the 
home  signal,  should  it  be  indicating  stop,  with  the 
possibility  of  there  being  a  collision  should  there 
be  another  train  in  the  block, 


RAILROAD  SIGNALING  39 

With  the  braking  distance  determined  for  the 
maximum  speed  allowed,  and  the  signals  so  located, 
the  time  interval  spacing  between  trains  will  be  a 
matter  of  the  time  it  will  take  a  train  to  run  through 
the  block,  plus  the  time  required  to  run  the  dis-- 


View  of  train  dispatcher's  office  showing  operators  using  tele- 
phone apparatus  adapted  to  train  dispatching. 


tance  between  the  distant  and  home  signals,  plus 
the  time  required  for  the  train  to  run  its  entire 
length,  the  spacing  of  trains  for  the  braking  distance 
being  dependent  on  the  position  of  the  head  end 

of  the  train,  and  the  clearing  of  the  signals,  after 


40 


THE  A  B  C  OF 


the  passing  of  a  train,  being  controlled  by  the  rear 
end  of  the  train.  In  addition,  time  must  be  added 
for  the  home  and  the  distant  signals  to  change 
from  the  stop  and  cautionary  to  the  clear  position 
and  the  time  required  by  the  engineman  to  observe 


A   mechanical   interlocking  plant,   showing   lead-out  in  front  of 
tower. 


that  the  signals  are  indicating  proceed  and  to  gov- 
ern the  train  accordingly.  This  last  interval  of  time 
may  be  considered  as  the  personal  equation  of  the 
engineman  and  will  vary  with  different  men.  With 
comparatively  slow  speed  trains,  5  to  8  seconds 
should  be  sufficient,  and  for  fast  trains  8  to  12 


RAILROAD  SIGNALING 


41 


seconds  interval  will  be  required  by  the  engineman 
to  assure  himself  that  he  may  continue  to  run  the 
train  at  speed,  after  observing  that  the  distant 
signal  has  changed  to  indicate  proceed.  With  allow- 
ances made  for  each  of  the  above  mentioned  de- 


interior  of  tower,   showing   levers  and   indicators.     The   inter- 
locking machine  is  of  the  vertical  locking  type. 


ments  which  enter  into  the  problem  of  determining 
the  maximum  number  of  trains  that  may  be  run  in  a 
given  time,  and  taking  the  sum  of  the  whole,  a 
chart  may  easily  be  plotted  showing  the  time  spac- 
ing of  trains  for  various  speeds  and  lengths  of  block. 
In  making  plans  for  and  discussing  with  the  operat- 


42  THE  A  B  C  OF 

ing  department  the  effects  on  the  traffic  of  any  pro- 
posed installation  of  signals,  this  chart  will  be 
found  of  great  convenience  to  the  signal  engineer. 

The  block  signals  which  have  been  described  in- 
dicate the  condition  of  but  one  track,  showing 
whether  or  not  this  track  is  occupied,  and  if  it  is 
proper  for  a  train  to  proceed.  Interlocking  signals, 
on  the  other  hand,  give  additional  information. 
They  show  the  route  which  a  train  may  take,  indi- 
cate the  speed  at  which  a  train  may  run,  show  if 
it  is  proper  for  the  train  to  proceed,  and  may  also 
be  arranged  to  show  if  the  track  is  unoccupied. 
The  necessity  for  indicating  the  route,  and  the  speed 
at  which  a  train  may  run,  is  evident  where  there 
are  facing  switches  in  a  main  track.  Interlocking 
signals  were  first  used  to  indicate  the  route  which 
a  train  would  be  required  to  take,  but  with  the  in- 
stallation of  the  narrow  angle  frogs  and  long  cross- 
overs or  turnouts,  enabling  trains  to  run  through 
switches  at  comparatively  high  speed,  it  has  be- 
come necessary  to  give  a  separate  signal  indication 
to  enable  an  engineman  to  assure  himself  it  is  safe 
to  run  at  the  speed  possible  through  these  long 
switches. 

In  order  to  insure  that  the  proper  route  will  be 
set  when  a  certain  signal  is  cleared  it  is  necessary 


RAILROAD  SIGNALING 


4:; 


that  the  switches  be  controlled  and  worked  by  the 
person  working  the  signals  governing  such  route, 
and  that  this  end  may  be  secured,  interlocking  ma- 


The  interlocking  itself.  The  pointed  dogs  sliding  into  and  out 
of  the  V-shaped  notches  in  a  certain  pre-determined  order  pre- 
vent mistakes  on  the  part  of  the  lever  man. 


chines  have  been  designed  which,  by  interlocking 
one  lever  with  the  others  which  control  the  move- 
ments of  the  signals  and  switches,  render  it  im- 
possible to  set  the  route  and  at  the  same  time  clear 


44 


THE  A  B  C  OF 


signals  for  movements  on  any  two  tracks  which 
conflict  and  may  result  in  two  trains  being  brought 
into  collision  with  each  other.  In  addition  to  the 
interlocking  between  the  levers,  it  is  necessary  to 


A  close  view  of  a   lead-out  of  the  rocker-shaft  type. 


insure  correspondence  in  working  between  the  lev- 
ers controlling  a  signal  or  switch  and  the  movement 
of  the  signal  or  switch  itself.  If  this  were  not  done 
the  lever  might  be  in  one  position,  allowing  a  cer- 
tain route  to  be  set  up,  and  the  signal  controlled 


RAILROAD  SIGNALING 


45 


by  such  lever  might  be  in  the  clear  position,  giving 
permission  for  a  movement  that  may  conflict  with 
a  train  moving  over  the  route  set.  This  corre- 


A  pipe-run.  Each  pipe  extends  to  a  switch  or  signal,  or  lock, 
and  is  connected  to  a  lever  in  the  tower,  transmitting  the  move- 
ment of  that  lever  to  the  proper  function. 


spondence  of  the  movement  of  the  controlled  func- 
tion with  the  lever  is  assumed  in  the  case  of  me- 
chanical interlocking  connections,  and  is  given  by 


46  THE  A  B  C  OF 

special  indicating  devices  in  the  case  of  power  oper- 
ated interlocking  signals  and  switches. 

Interlocking  signals  are  divided  into  three  gen- 
eral classes  based  upon  the  means  employed  to  work 
the  various  functions  controlled  from  the  interlock- 
ing machine.  In  a  mechanical  interlocking  the  func- 
tions are  connected  to  the  levers  by  pipe  and  some- 
times, in  the  case  of  signals,  by  steel  wire.  The 
electro-pneumatic  type  of  interlocking  makes  use 
of  compressed  air  to  work  the  switches  and  signals, 
and  the  movement  of  these  functions  is  controlled 
by  electro  magnets,  the  same  as  with  the  block 
signals  of  this  type  of  apparatus.  In  the  electric 
interlocking  system  the  signals  and  switches  are 
worked  by  direct  current  obtained  from  generators, 
or  from  storage  batteries,  the  switches  being  worked 
by  motors  and  the  signals  by  motors  or  by  solenoid 
coils. 

With  the  mechanical  interlocking  the  connections 
between  the  levers  and  the  signals,  switches  or 
locks  are  of  one  inch  pipe,  and  are  run  from  the 
lever  to  the  signal  or  switch  to  be  worked.  To  pre- 
vent the  pipe  from  bending,  carriers  are  placed  every 
7  feet  apart,  and  turns  or  changes  in  direction  of 
the  line  are  made  by  means  of  cranks  arranged  on 


RAILROAD  SIGNALING 


47 


The   pipe-run   on   the  other  side  of  the  tower. 


48 


THE  A  B  C  OF 


suitable  foundations.  Changes  in  the  length  of  the 
connections  are  taken  care  of  by  means  of  com- 
pensators, which  must  be  put  midway  between  the 
lever  and  the  end  of  the  pipe  line.  One  switch,  or 
in  the  case  of  a  crossover,  two  switches  may  be 


A   dwarf   signal   at   a   mechanical    interlocking   plant. 


worked  by  one  lever.  Another  lever  must  be  used 
to  work  the  switch  point  lock  by  which  the  switches 
are  locked  and  held  after  being  moved  into  proper 
position  by  the  lever  from  which  they  are  worked. 
The  signals  in  the  rear  of  the  switches  are  known 


RAILROAD  SIGNALING 


49 


as  home  signals  for  movements  on  a  line  with  the 
direction  of  traffic,  and  are  placed  on  high  signal 
poles.  Movements  on  main  lines  in  the  reverse  di- 
rection of  traffic,  and  on  or  from  sidings  and  yard 
tracks  are  placed  on  short  posts  about  18  inches 
above  the  top  of  the  tie,  and  are  known  as  dwarf 


A  "Clear"  signal. 


signals.  Distant  signals  placed  in  the  rear  of  the 
home  signal  a  distance  in  excess  of  the  braking  dis- 
tance for  the  maximum  speed  allowed,  are  used  to 
repeat  the  proceed  indication  of  all  of  the  home 
signals,  and  being  further  away  than  can  advanta- 
geously be  worked  by  mechanical  connections,  are 
power  operated,  being  worked  by  a  motor  taking 


50 


THE  A  B  C  OF 


current  from  a  battery  of  16  cells  placed  approxi- 
mately at  the  base  of  the  signal  pole.  Each  signal 
of  an  interlocking  should  be  worked  by  a  separate 


Showing   method  of  transmitting   motion  from   pipe-run  on  the 
ground  to  signals  on  a  bridge. 


lever  as  giving  greater  reliability  in  operation,  and 
relieving  the  signalman  of  the  necessity  of  checking 
the  position  of  the  switch  levers,  to  insure  that  the 
desired  route  is  set  before  a  signal  is  cleared.  For 


RAILROAD  SIGNALING 


51 


this  reason,  the  use  of  selectors  by  which  one  or 
more  signals  are  operated  by  one  lever,  is  being 
given  up.  For  interlocking  plants,  where  the 
switches  are  reasonably  close  to  the  tower,  and  there 
is  ample  space  in  which  to  run  the  connections  with 


An   interlocked  double-slip  switch. 


good  drainage,  a  mechanical  machine  is  considered 
as  reliable  and  safe  working,  besides  being  the  most 
economical  to  maintain  of  any  that  are  now  in  gen- 
eral use. 

The   electro-pneumatic   interlocking  system   uses 


52 


THE  A  B  C  OF 


compressed  air  at  75  to  100  pounds  pressure  to  work 
the  switches  and  signals.  One  or  two  switches  may 
be  worked  by  one  lever.  The  unlocking,  the  mov- 
ing and  the  relocking  of  a  switch  are  all  performed 
by  the  switch  movement,  which  is  operated  by  a 
piston  moving  in  a  cylinder  to  which  compressed 


An    interlocking    switch,    showing   a   facing    point    lock. 


air  is  admitted  when  the  switch  is  to  be  moved. 
The  indication  by  which  assurance  is  given  at  the 
machine,  that  the  movement  has  completed  its 
stroke,  is  given  by  contact  springs  attached  to  the 
movement,  a  separate  circuit  being  used  to  lock  the 
lever  and  prevent  the  completed  movement  being 
made  until  the  indication  has  been  received  at  the 


RAILROAD  SIGNALING 


53 


machine.  The  signals  are  of  the  same  form  and 
type  as  used  for  the  electro-pneumatic  block  sig- 
nals. An  indication  circuit  is  provided  to  insure  that 
the  signal  has  been  returned  to  the  stop  position  be- 
fore the  signal  lever  may  be  placed  normal  and  un- 


An   interlocking   derail,   showing   a  switch   and  lock  movement. 


lock  the  other  levers  of  the  route  governed  by  the 
signal. 

Where  an  electro-pneumatic  interlocking  is  in- 
stalled on  a  line  equipped  with  electro-pneumatic 
signals,  the  compressed  air  supply  may  be  obtained 


54  THE  A  B  C  OF 

from  the  main  pipe  in  use  at  such  point,  but  in  the 
case  of  isolated  plants  an  air  compressor  equipment 
in  duplicate  must  be  put  in.  If  steam  may  be  ob- 
tained from  a  nearby  power  station,  steam  operated 


A   small    interlocking  tower.      Governs   a  single  track  crossing. 

air  compressors  are  generally  used,  but  if  not,  gaso- 
line or  oil  engines  should  be  put  in  for  the  purpose. 
The  all  electric  type  of  interlocking  is  the  one  of 
most  recent  development.    With  this  type,  an  elec- 


R.  If 'L ROAD  SIGNALING 


5,-) 


trie  motor  is  used  to  work  a  switch  or  a  signal.  Sev- 
eral mechanisms  have  been  designed  to  work  these 
functions,  but  the  most  common  is  that  where  the 
high  speed  of  the  motor  armature  is  reduced  by 
means  of  gears  to  the  slow  speed  required  to  turn 
an  escapement  crank  which  in  turn  unlocks  a  switch, 
moves  the  switch  and  relocks  it.  A  valuable  feature 
of  such  a  system  is  the  changing  of  the  motor  into 


Principle  of  interlocking  for  Saxby  &  Farmer  machines.  In  the 
diagram  lever  1,  when  reversed,  i.  e.,  moved  to  the  right,  will 
lock  lever  2  in  its  normal  position  if  lever  3  is  reversed. 


a  generator  by  reversing  the  connections,  after  the 
switch  has  been  moved,  and  using  the  current  so 
generated  to  energize  the  indication  magnets  to  re- 
lease the  switch  lever.  A  saving  is  thereby  effected 
in  wire  connections  and  current  is  supplied  to  these 
wires  to  give  the  indication  only  after  the  move- 
ment of  the  switch  has  been  completed.  The  giving 
of  an  indication  by  this  means  is  known  as  the 


56  THE  A  B  C  OF 

"dynamic"  method  as  distinguished  from  the  bat- 
tery form  of  indication.  So  also  with  the  signal 
movement  the  restoring  of  the  mechanism  to  the 
normal  position  is  made  to  generate  current  to  give 
the  indication  at  the  interlocking  machine  and  re- 
lease the  lever  only  after  the  signal  has  been  re- 
turned to  the  stop  position. 

The  power  equipment  for  the  electric  interlocking 
is  less  expensive  than  for  the  electro-pneumatic,  as 
the  movement  of  a  switch  or  signal  is  completed 
in  one  or  two  seconds,  after  which  the  current  is 
shut  off  until  the  switch  is  again  to  be  moved.  It 
is  therefore  possible  to  charge  storage  batteries 
and  run  a  plant  of  moderate  size  for  four  days  or 
a  week  with  but  one  charging  of  the  batteries,  which 
may  be  of  comparatively  small  size,  as  may  also  be 
the  size  of  the  generator  and  gasoline  engine  with 
which  current  is  obtained  to  charge  the  batteries. 

In  the  operation  of  a  switch  from  the  lever  of  an 
interlocking  machine,  it  is  essential  for  safe  work- 
ing that  a  switch  must  not  be  thrown  under  a  train, 
whether  the  train  be  running  through  the  switch 
in  a  facing  or  a  trailing  direction.  To  prevent  this 
being  done  detector  bars  are  made  use  of.  These 
bars  are  formed  of  2j^x^  or  y2  inch  steel,  arranged 


RAILROAD  SIGNALING 


Sectional  diagram  and  principal  dimensions  of  Saxby  &  Farmer 
interlocking   machine. 


58  THE  A  B  C  OF 

on  edge  on  the  outside  of  the  head  of  the  rail.  In 
its  normal  position,  with  the  top  edge  of  the  bar 
below  the  top  of  the  rail,  the  bar  is  not  touched 
by  the  wheels  of  passing  trains.  The  bars  are  held 
in  position  by  means  of  clips  and  links,  so  arranged 
that  when  the  bar  is  moved,  the  top  of  the  bar  is 
raised  about  1/4  of  an  inch  above  the  top  of  the 
rail.  If  a  wheel  is  on  the  rail  above  the  bar,  the 
bar  will  be  prevented  from  changing  from  one  posi- 
tion to  the  other.  By  connecting  the  bar  to  the 
movement  working  or  locking  the  switch,  the  switch 
cannot  be  unlocked  and  thrown  when  there  is  a 
wheel  passing  or  standing  on  the  rail  and  project- 
ing above  the  detector  bar. 

With  the  100  pound  rails  with  wide  heads,  now 
commonly  used,  all  wheels  of  a  train  do  not  pro- 
ject over  the  top  of  the  detector  bar  sufficiently 
to  insure  in  all  cases  against  the  bar  being  thrown 
under  a  train,  and  it  is  now  becoming  customary 
to  use  electric  locking  of  the  switch  levers  as  a 
substitute  for  the  detector  bars.  This  locking  may 
readily  be  performed  by  making  the  section  of 
track,  in  which  the  switch  or  switches  it  is  desired 
to  protect  are  located,  into  a  track  circuit  and  con- 
trolling the  lock  on  the  switch  lever  by  this  cir- 


RAILROAD  SIGNALING  59 

cuit.  If  the  track  is  occupied  the  lever  will  be 
locked  and  cannot  be  thrown.  This  method  has 
been  found  to  be  more  effective  than  detector  bars, 
as  if  the  lever  is  pulled  when  it  should  not  be,  the 
lock  will  take  the  strain  much  better  than  a  bar 
which  might  slip  by  the  edge  of  a  wheel  or  even 
be  broken  by  the  wheel,  allowing  the  switch  to  be 


An    electro-pneumatic    interlocking    machine. 

changed  under  the  train.  By  arranging  an  indica- 
tor to  show  when  a  section  of  track  is  occupied, 
and  connecting  it  to  the  circuit  controlling  the  lock 
on  the  lever,  an  indication  is  given  of  the  approx- 
imate position  of  a  train  that  may  be  occupying 
any  part  of  the  track  within  the  limits  of  the  in- 
terlocking, and  the  signalman  will  know,  without 
trying  a  lever,  whether  or  not  the  lever  may  be 


60  THE  A  B  C  OF 

moved  and  the  switch  changed.  A  number  of  re- 
lays are  required  for  the  circuits  of  even  a  small 
plant. 

Electric  locking,  although. preventing  the  chang- 
ing of  the  switch  after  a  train  has  run  on  the  track 
circuit,  thereby  shunting  the  relay  and  locking  the 
lever,  is  not  effective  in  holding  the  lever  when 
the  track  circuit  section  is  unoccupied.  It  has  at 
times  occurred  that  the  signalman,  after  setting  up 
a  route  and  clearing  the  signals  for  an  approach- 
ing train,  has  improperly  changed  the  signals  to 
indicate  stop  and  opened  a  switch  changing  the 
route  immediately  ahead  of  the  train,  with  the  occa- 
sional result  of  derailing  the  train  or  causing  it  to 
come  into  collision  with  another.  To  guard  against 
the  signalman  making  a  mistake  of  the  kind,  and 
an  engineman  claiming,  in  case  of  an  accident,  that 
the  signal  had  been  taken  away  from  him,  a  system 
of  approach  locking  has  been  devised,  which  locks 
the  route  for  which  a  signal  has  been  cleared,  from 
the  time  the  train  arrives  at  the  track  circuit  in  the 
rear  of  the  distant  signal  until  the  head  end  of  the 
train  passes  a  home  signal  and  will  have  run  on 
the  switch  locking  track  circuit,  locking  the  switch 
and  preventing  a  change  of  the  route.  In  addition 


RAILROAD  SIGNALING  61 

to  forming  an  approach  lock  on  the  signal  lever,  the 
arrangement  is  made  to  serve  as  an  indicator  an- 


A   group   of  relays   and   storage   batteries   governing   automatic 
signal  circuits. 


nouncing  the  approach  of  a  train  and  calling  the 
attention    of   the   signalman    to   the    fact    that    the 


62  THE  ABC  OP 

signals  should  be  cleared  for  the  oncoming  train 
to  proceed. 

With  the  increase  from  double  to  3  or  4  main 
tracks,  the  number  of  signals  required  at  an  inter- 
locking to  indicate  the  route  set  has  greatly  in- 
creased, and  with  the  increase  in  speed  the  neces- 
sity has  arisen  of  indicating  to  an  engineman  the 
speed  at  which  the  train  may  run,  in  addition  to  the 
route  the  train  is  expected  to  take.  To  enable  an 
engineman  to  run  at  speed  through  an  interlocking, 
it  is  necessary  that  a  distant  signal  indication,  in 
addition  to  the  home  signal,  be  given  for  each  route 
on  which  limited  and  normal  speeds  may  be  run. 

With  the  ordinary  two-position  signal,  which  in 
the  horizontal  position  indicates  stop  or  caution, 
and  in  the  downwardly  inclined  position  indicates 
proceed,  three  home  signal  arms  will  be  required  on 
each  pole,  and  in  addition  two  distant  signal  arms, 
one  to  repeat  the  indication  of  the  next  signal  in 
advance  on  the  normal  speed  track,  and  the  other 
the  indication  of  the  next  home  signal  in  advance 
on  the  limited  speed  route.  This  would  call  for 
the  installation  on  these  signals  of  five  arms,  which 
is  objectionable  from  the  difficult  and  expensive 
construction  involved,  and  from  the  fact  that  it  is 


R.\ILRO.\n  SIGNALING  63 

confusing  to  the  enginemen  to  have  to  observe  so 
many  arms  and  lights,  and  mistakes  may  result. 
The  practice  was  therefore  begun  a  number  of 
years  ago  of  dispensing  with  the  distant  arms  and 


A  group  of  indicators  in  a  tower.  By  means  of  these  indi- 
cators a  tower-man  is  enabled  to  note  at  a  glance  the  positions 
of  trains  on  the  tracks  governed  by  his  machine. 


64  THE  A  B  C  OF 

making  the  home  signal  arm  travel  indicate  pro- 
ceed and  to  use  the  45  degree  or  middle  stroke  posi- 
tion of  the  arm  to  indicate  caution  when  repeating 
the  stop  indication  of  the  next  home  signal  in  ad- 
vance. With  this  arrangement  of  signals  three 
arms  would  be  the  maximum  required  for  a  single 
pole,  and  in  addition  to  indicating  routes,  speeds 
could  also  be  indicated  by  having  the  top  arm 
cleared  only  for  the  main  line  or  normal  speed  route, 
the  second  arm  for  the  limited  speed  route  to  an- 
other track  with  traffic,  and  the  third,  the  lowest 
arm,  to  indicate  proceed  for  any  route  whether 
there  was  a  signal  in  advance  and  whether  or  not 
the  track  was  occupied. 

In  using  the  arm  in  the  vertical  position  to  indi- 
cate proceed,  it  was  found  that  the  arm  was  not 
as  easily  distinguishable  as  when  occupying  the  60 
degree  position,  and  it  was  recommended  that  the 
arm  be  moved  upwardly  from  the  horizontal  posi- 
tion to  give  the  cautionary  and  proceed  indications. 
This  was  merely  a  return  to  the  arrangement  used 
in  the  early  days  of  railroading,  and  now  used  in  a 
modified  way  in  Germany.  In  addition  to  making 
the  signal  more  distinguishable,  greater  safety  in 
operation  will  result  from  moving  the  signal  up- 


RAILROAD  SIGNALING 


65 


wardly  from  the  horizontal  position,  as  should  there 
be  an  accumulation  of  ice  or  snow  on  the  parts  or 
the  mechanism  become  disconnected  from  the  sig- 


An    electric    interlocking    machine. 


nal,  the  weight  of  the  spectacle  and  blade  would 
act  to  return  the  signal  to  the  position  to  give  the 
stop  indication.  On  account  of  these  advantages 
the  Railway  Signal  Association  has  recommended. 


66  THE  A  B  C  OF 

and  a  number  of  roads,  among  them  the  New  York 
Central  and  the  Boston  &  Albany,  have  adopted 
this  new  universal  system  of  signaling,  whereby  the 
arms  move  upwardly  to  give  the  caution  and  pro- 
ceed indications,  with  the  45  degree  position  indi- 
cating caution,  the  vertical  position  proceed,  and 
with  the  upper  arm  governing  movements  to  be 
made  at  normal  sp^ed^  the  second  arm  of  a  signal 
tc  govern  movements  to  an  adjacent  track  at  lim- 
ited speed  and  with  traffic,  and  the  third  arm  for  a 
movement  to  any  route  for  which  the  switches  may 
be  set.  The  lights  at  night  on  a  home  signal  giv- 
ing a  "Stop  and  stay  until  authorized  to  proceed" 
indication  are  arranged  in  a  vertical  line ;  on  an 
automatic  signal  which,  when  in  the  stop  position 
indicates  "Stop  and  then  proceed  with  caution," 
the  lights  are  diagonally  arranged  on  the  pole  and 
with  the  train  order  signal  which  indicates  "Stop 
within  defined  limits,  there  are  orders  for  you,"  the 
lights  are  horizontally  arranged,  at  least  two  lights 
being  used  on  each  signal  irrespective  of  the  num- 
ber of  arms  on  the  pole. 

Up  to  the  present  time  block  and  interlocking 
signal  systems  for  surface  railroads  are  designed 
and  operated  on  the  assumption  that  the  engine- 


RAILROAD  SIGNALING       .  67 

man  will  obey  the  indications  of  the  signals  and 
safe  working  will  result.  However,  it  is  a  fact  that 
enginemen,  like  other  human  beings,  occasionally 
make  mistakes,  go  to  sleep  on  duty,  forget  what 
they  are  doing  and  instead  of  always  observing  the 
caution  indication  of  the  distant  signal  and  the 
stop  indication  of  the  home  signal,  will  pass  the 
home  signal  without  stopping,  with  the  possibility 
of  a  derailment  or  a  collision  occurring  with  another 
train.  In  the  endeavor  to  perfect  a  satisfactory 
cab  signal  and  an  automatic  stop  or  train  control 
device,  which  will  compel  the  engineman  to  obey 
a  stop  signal  indication,  a  number  of  devices  and 
forms  of  apparatus  have  been  patented  and  the  at- 
tempt made,  through  public  opinion,  to  force  the 
railroads  to  use  one  or  more  of  these  for  the  safe- 
guarding of  traffic.  Up  to  the  present  time,  a  num- 
ber of  train  control  devices  have  been  given  a  trial 
in  actual  service,  but  not  one  is  in  general  use  on  a 
surface  railroad  in  the  United  States,  although  they 
have  been  introduced  to  a  limited  extent  in  Eng- 
land and  are  in  successful  use  on  roads  having 
special  traffic,  such  as  the  elevated  line  in  Boston 
and  on  the  subway  and  the  Hudson  terminal  lines 
in  New  York.  One  automatic  stop  system  has 


68 


THE  A  B  C  OF 


been  tested  on  a  western  road  and  is  being  officially 
observed  by   the  Block   Signal   and  Train   Control 


A  double  automatic  signal   location  on  single  track. 

Board  of  the  Interstate  Commerce  Commission,  but 
has  not  yet  been  in  use  long  enough  to  show  what 


RAILROAD  SIGNALING  60 

it  will  do  under  all  conditions  of  weather.  So  many 
of  these  devices  have  been  brought  out  by  men 
who  would  save  millions  for  railroads  by  prevent- 
ing accidents,  but  which  are  so  impracticable  and 
impossible  of  operation,  a  committee  of  the  Rail- 
way Signal  Association  has  submitted  to  its  mem- 
bers for  adoption  a  set  of  requisites  of  installation 
for  these  devices  which  should  be  complied  with 
before  a  given  device  may  be  considered  as  fulfill- 
ing the  requirements  for  the  safe  and  proper  opera- 
tion of  trains. 

The  rules  under  which  signals  are  used  and  main- 
tained are  a  very  important  feature  in  the  operation 
of  the  railroad  and  have  a  great  deal  to  do  with  the 
successful  use  of  the  signals.  Rules  governing  the 
operation  and  use  of  the  different  types  of  signals 
and  signal  systems  in  service  on  a  given  road,  must 
be  prepared  for  and  observed  by  the  men  in  the 
operation  of  the  trains.  In  a  general  way.  rules 
should  be  framed  governing  the  observance  of  and 
the  use  of  the  various  types  of  signals,  the  rules  for 
each  class  of  employes,  those  for  the  train  and  en- 
gine crews,  and  those  for  the  signalmen  being 
worded  to  cover  the  exact  duties  to  be  performed 
by  each.  The  rules  should  also  cover  such  fea- 


TO 


tures  as  the  definitions,  types  of  signals,  signal  as- 
pects and  indications,  principles  of  signal  loca- 
tions, general  rules  to  be  followed  in  the  use  of  all 
classes  of  signals  and  detail  rules  for  the  use  and 


Section    of    electro-pneumatic    interlocking    machine,    showing 
also  indicators  and  train  announcing  devices. 


observance  of  particular  systems  and  special  signals. 

The  matter  of  estimates  for,  and  the  cost  of  signal 

work,   is   a  most  important  one   and  must  receive 

especial  attention  on  the  part  of  the  signal  engineer. 


RAILROAD  SIGXALIXC,  71 

In  nearly  every  instance,  before  work  is  authorized, 
an  estimate  of  the  cost  must  be  made  by  the  signal 
engineer,  and  where  contracts  are  to  be  let  an  en- 
gineer's estimate  should  be  made  as  a  check  of  the 
bids  to  be  made  by  the  contractors.  For  the  parts 
to  be  seen  by  the  casual  observer,  and  even  to 
many  operating  officials,  signal  work  is  considered 
as  costing  in  proportion  more  than  any  other  part 
of  the  equipment  of  a  road.  The  reason  for  this  is 
largely  due  to  the  expensive  materials  used,  the  cop- 
per and  rubber  in  insulated  wires,  and  the  finely 
finished  mechanisms  required  for  the  interlocking 
machines,  signals  and  relays.  The  electrical  attach- 
ments and  adjuncts  to  an  ordinary  mechanical  in- 
terlocking very  nearly  double  the  cost  of  the  installa- 
tion without  any  apparent  increase  in  the  equip- 
ment, so  far  as  is  observed  by  those  not  familiar 
with  the  details  of  the  installation.  The  criticism 
has  been  made  that  these  additional  safeguards 
might  profitably  be  dispensed  with  and  the  money 
used  in  extending  the  simpler  forms  of  signal  pro- 
tection. While  possibly  this  may  be  true  in  excep- 
tional instances,  such  practice  will  not  be  advisable 
until  operating  officials  and  the  public  recognize 
that  the  enginemen  and  the  sigalmen  should  be  so 


72 


THE  A  B  C  OF 


trained  that  they  will  perform  their  duty  regularly, 
properly  and  without  fail  and  that  it  is  not  neces- 
sary to  so  perfect  the  signal  system  that  wrong 
movements  and  collisions  must  be  prevented  irre- 
spective of  whether  the  men  do  as  they  should  or 


A   typical    signal    bridge. 


fail  to  act  in  accordance  with  the  indications  given 
by  the  -signals. 

The  number  of  signals  now  in  use,  and  the  forces 
employed  in  installation  and  maintenance  are  so  large 
the  signal  department  of  a  road  is  becoming  more 


RAILROAD  SIGNALING  73 

and  more  specialized  and  increasing  in  importance 
as  this  occurs.  The  signal  department  on.  various 
roads  is  organized  in  almost  as  many  different  ways 
as  there  are  roads,  but  as  with  many  other  depart- 
ments they  are  generally  arranged  on  a  depart- 
mental plan  for  roads  having  comparatively  few 
signals,  and  on  a  divisional  basis  on  large  roads 
which  are  well  equipped  with  signals.  In  the  de- 
partmental organization  the  signal  engineer  is 
usually  in  complete  charge  of  the  department,  hav- 
ing control  of  the  construction  and  maintenance 
forces,  and  acting  in  an  advisory  capacity  on  signal 
matters  to  the  general  manager,  the  general  super- 
intendent or  the  chief  engineer,  as  the  case  may  be. 
The  signal  engineer  has  charge  of  the  stock  carried, 
makes  requisitions  for  signal  material,  has  charge 
of  the  signal  accounts,  causes  investigations  to  be 
made  of  signal  failures,  reporting  to  and  conferring 
with  the  operating  department  in  cases  where  acci- 
dents have  occurred  and  the  signals  are  involved. 

With  a  divisional  organization  the  signal  work 
on  a  division  is  usually  put  in  charge  of  a  signal 
supervisor,  who  reports  to  the  division  superintend- 
ent, and  in  matters  pertaining  to  the  maintenance 
of  signals,  and  sometimes  in  the  installation  of  new 


74  THE  A  B  C  OF 

signals,  acts  practically  as  the  signal  engineer  for 
the  division.  The  signal  engineer  on  such  roads 
then  becomes  a  staff  officer,  acting  in  an  advisory 
capacity  to  the  general  manager,  general  superin- 
tendent or  chief  engineer,  as  may  be  arranged.  He 
is  usually  charged  with  the  making  of  signal  stand- 
ards, making  or  approving  plans  for  new  installa- 
tions and,  in  many  cases,  contracting  for  and  super-' 
vising  new  installations  that  are  made. 

The  signal  engineer,  to  be  successful  in  his  work, 
must  be  a  man  with  an  extended  knowledge  of  the 
details  of  the  business,  and  have  exceptional  quali- 
fications in  the  matter  of  handling  men,  good  busi- 
ness ability,  particularly  in  accounting  matters,  be 
well  posted  on  train  operation  and  the  movement 
of  trains  at  special  points.  He  should  be  able  to 
advise  his  superior  officer  in  regard  to  operating 
practice  and  to  write  or  to  revise  signal  rules.  He 
must  be  well  posted  on  track  work,  for  when  a 
switch  is  connected  to  and  worked  from  an  inter- 
locking, the  signal  department  becomes  responsible 
for  the  adjustment  of  the  switch. 

The  signal  engineer  should  have  a  knowledge  of 
paints  and  painting,  cements  and  concrete  work, 
blacksmithing,  pipe  fitting,  be  a  machinist  as  well 


RAILROAD  SIGNALING  75 

as  a  draftsman,  be  capable  of  making  designs  of 
mechanical  apparatus  and  constructing  the  same, 
and  lastly  and  almost  of  the  most  importance  he 
should  be  an  electrical  engineer.  There  is  not,  to 
my  knowledge,  a  department  of  railroad  work  in 
which  the  men  are  required  to  have  an  expert 
knowledge  of  their  own,  as  well  as  of  the  work  of 
other  departments,  as  is  the  case  with  the  signal 
department,  and  with  the  advance  in  the  art  and 
science  of  signaling,  the  work  of  the  signal  engineer 
will  increase  rather  than  decrease,  and  he  will  be 
given  that  recognition  which  the  work  he  is  called 
upon  to  perform  most  properly  entitles  him  to. 


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